/*
	PIP - Platform Independent Primitives

	Stephan Fomenko

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "pithreadpoolexecutor.h"
#include "pisysteminfo.h"

/*! \class PIThreadPoolExecutor
 * @brief Thread pools address two different problems: they usually provide improved performance when executing large
 * numbers of asynchronous tasks, due to reduced per-task invocation overhead, and they provide a means of bounding and
 * managing the resources, including threads, consumed when executing a collection of tasks.
 */


PIThreadPoolExecutor::PIThreadPoolExecutor(size_t corePoolSize, PIBlockingDequeue<std::function<void()> > * taskQueue_) : isShutdown_(false) {
	queue_own = false;
	if (corePoolSize <= 0)
		corePoolSize = PISystemInfo::instance()->processorsCount;
	if (!taskQueue_) {
		taskQueue = new PIBlockingDequeue<std::function<void()> >();
		queue_own = true;
	}
	for (size_t i = 0; i < corePoolSize; ++i) {
		PIThread * thread = new PIThread([&, i](){
			auto runnable = taskQueue->poll(100, std::function<void()>());
			if (runnable) {
				runnable();
			}
			if (isShutdown_ && taskQueue->size() == 0) threadPool[i]->stop();
		});
		threadPool.push_back(thread);
		thread->start();
	}
}


bool PIThreadPoolExecutor::awaitTermination(int timeoutMs) {
	PITimeMeasurer measurer;
	for (size_t i = 0; i < threadPool.size(); ++i) {
		int dif = timeoutMs - (int)measurer.elapsed_m();
		if (dif < 0) return false;
		if (!threadPool[i]->waitForFinish(dif)) return false;
	}
	return true;
}


void PIThreadPoolExecutor::shutdownNow() {
	isShutdown_ = true;
	for (size_t i = 0; i < threadPool.size(); ++i) threadPool[i]->stop();
}


PIThreadPoolExecutor::~PIThreadPoolExecutor() {
	shutdownNow();
	while (threadPool.size() > 0) delete threadPool.take_back();
	if (queue_own)
		delete taskQueue;
}


void PIThreadPoolExecutor::execute(const std::function<void()> & runnable) {
	if (!isShutdown_) taskQueue->offer(runnable);
}


bool PIThreadPoolExecutor::isShutdown() const {
	return isShutdown_;
}


void PIThreadPoolExecutor::shutdown() {
	isShutdown_ = true;
}